Sickle Cell Disease (SCD) Quick Overview

Sickle cell disease is the most common of the hereditary blood disorders. It occurs almost exclusively among black Americans and black Africans.

Sickle cell disease in black Americans occurs in about 1 in 500 live births.

The first account of what was then called sickle cell anemia in the medical literature was in 1910. James B. Herrick, a Chicago physician, described the symptoms of a 20-year-old black male student from the West Indies. The man had reported "shortness of breath, palpitations, and episodes of icterus [yellow eyes]. He had an anemia." Dr. Herrick described the patient's blood smear as showing "thin, sickle-shaped and crescent-shaped red cells."

Red blood cells deliver oxygen to working or active tissues. In the lungs, hemoglobin (the molecule in the red blood cell) takes on oxygen and, at the same time, releases carbon dioxide. This process is called oxygenation. At the tissue level, this activity is reversed. The same hemoglobin molecule releases oxygen and takes on carbon dioxide. This process is called deoxygenation.

In sickle cell disease, certain red blood cells become crescent-shaped (the sickle cell Dr. Herrick described). These abnormal red blood cells, carrying an abnormal hemoglobin known as hemoglobin S, are fragile. A person who has sickle cell disease can become more likely to get infections because the damaged cells eventually clog the spleen. A severe attack, known as sickle cell crisis, can cause pain because blood vessels can become blocked or the defective red blood cells can damage organs in the body. There is also an impairment in oxygentation from the abnormal hemoglobin S.